Tsunami generation by landslides and extreme runup heights

Speaker: Hermann Marc Fritz
Tsunamis are commonly associated with submarine earthquakes, such as the 2004 Indian Ocean tsunami. Tectonic tsunamis are limited in wave height by the seafloor displacement. For some earthquakes, such as the 1998 Papua New Guinea and 2006 Java tsunamis, it has been proposed that the large tsunamis were triggered by massive failure of the sea floor in the form of giant submarine landslides. Landslide and volcanic eruption generated tsunamis are typically regionally confined but account for all known localized runup heights exceeding 100 m in the past century: Lituya Bay, Alaska, Vajont Reservoir, Italy and Spirit Lake, Mount St. Helens. Other localized runup heights exceeding 50m have been recorded on Shimabara peninsula and several fjords in Norway and Chile among others. The largest mega-tsunami runup dates back to 10 July 1958, when an earthquake of Mw 8.3 at the Fairweather Fault triggered a rockslide into Lituya Bay. The rockslide impact generated a giant tsunami at the head of Lituya Bay resulting in an unprecedented tsunami runup of 524 m marked by forest trim line and erosion down to bedrock. The mega-tsunami runup is studied with a hybrid modeling approach applying both physical and numerical models of slide processes of deformable bodies into a U-shaped trench similar to the geometry found at Lituya Bay. Tsunami generation by landslides were also studied in the three dimensional NEES (Network for Earthquake Engineering Simulation) tsunami wave basin at OSU (Oregon State University) based on the generalized Froude similarity.